1. Field of the Invention
The invention provides an improved connection for sealably joining the ends of two conduits. More particularly, the invention relates to a leakproof union coupling for use in connecting conduits used in refrigeration systems.
2. Description of the Prior Art
Refrigeration systems may typically include several components, such as compressors, condensers, heat exchangers, and valves, which must be connected together in a way that effectively seals the interior of the refrigerant circulating system from the environment around it. Refrigerants, such as freon, which are introduced into such systems as the working fluid, are expensive, hazardous to the environment, and sometimes toxic, and it is therefore critical that a closed circulating system of a refrigeration system be effectively sealed to prevent escape of the fluid or gas.
Sealing of a refrigeration system is often complicated by the fact that various portions of a system are simultaneously hot and cold, and may be operated under a high pressure and a vacuum, and vibration is often a factor. Also, the common refrigerant fluids may be incompatible with many common sealing materials, and specialized materials such as polytetrafluoroethylene (Teflon) must be used.
It is often desirable that a connection between two components of a refrigeration system be easily disconnectable, so that installation and replacement of a component may be accomplished without the use of heat connecting methods or extensive tools. It is also desirable that the connection be accomplished by abutting the ends of two fixed conduits and sealably joining them, without rotating either conduit. Connections known as "unions" are common in plumbing and other pipefitting arts, which employ a rotatable collar to connect abutting ends of conduits, where the ends have been previously fitted with appropriate hardware. The typical union may be repeatedly connected and disconnected by rotating the collar.
A typical union believed to partially satisfy the demanding requirements of refrigeration service, able to withstand the heat, cold, pressure, vacuum, vibration and exposure to refrigerant, was described in U.S. Pat. Nos. 2,934,915 and 3,091,945 in the late 1950's and continues to be used, incorporated into a "Rotalock" valve made by Primore Sales, Inc. of Adrian, Mich.
The Rotalock union establishes an effective seal with relatively little torque applied to the collar by providing two sealing surfaces which are held together by the collar. To effectuate an adequate seal, one of the sealing surfaces has an annular rib extending from it, while the other sealing surface has a complementary groove. In an early version, a malleable metal washer was positioned between the sealing surfaces and deformed by the rib/groove combination, providing a gas tight seal with the collar hand tightened.
Later versions, including one in use today, use a plastic ring placed in the groove. When the collar is tightened, it draws the rib into the plastic ring while the groove limits deformation of the ring, providing a high pressure seal.
The Rotalock union appears to exhibit several disadvantages, however. First, its components are believed to be relatively difficult and therefore expensive to fabricate, particularly the critical rib on the one side and groove on the other. These are typically rather small features that must be machined with precision. Second, its components also appear to be possibly subject to damage, again particularly the rib extending from one of the sealing surfaces. Third, if the rib is fully depressed into the plastic ring each time the connection is tightened, it appears that the ring may become indented or eroded to the point that the rib will no longer press into the ring with adequate force around the complete circle. A leak therefore might develop that would be correctable only by disassembling the union and replacing the ring, a process that may involve loss of refrigerant and increased costs.